NDC to Labeler Code Product Code Crosswalk

The FDA
describes the National Drug Code (NDC) Number in the following way:

"Each listed drug product listed is assigned a unique 10-digit, 3-segment number.
This number, known as the NDC, identifies the labeler, product, and trade package size.
The first segment, the labeler code, is assigned by the FDA.
A labeler is any firm that manufactures (including repackers or relabelers),
or distributes (under its own name) the drug.
The second segment, the product code, identifies a specific strength,
dosage form, and formulation for a particular firm.
The third segment, the package code, identifies package sizes and types.
Both the product and package codes are assigned by the firm.
The NDC will be in one of the following configurations: 4-4-2, 5-3-2, or 5-4-1."

"Since the NDC is limited to 10 digits, a firm with a 5 digit labeler code must choose
between a 3 digit product code and 2 digit package code,
or a 4 digit product code and 1 digit package code."

"Thus, you have either a 5-4-1 or a 5-3-2 configuration for the three segments of the NDC.
Because of a conflict with the HIPAA standard of an 11 digit NDC,
many programs will pad the product code or package code segments of the NDC
with a leading zero instead of the asterisk."

"Since a zero can be a valid digit in the NDC, this can lead to confusion when trying
to reconstitute the NDC back to its FDA standard.
Example: 12345-0678-09 (11 digits) could be 12345-678-09 or 12345-0678-9 depending on the firm's configuration."

The current deliveries
of the FDA's NDC data include the NDC variable. However, files from June 2, 2012
and earlier contain the three segments of the NDC variable rather than the NDC variable itself.

Jean Roth created the ndc to labeler code and product code crosswalk files below to address this.
The files are based on data from January 8, 2007 through June 2, 2012.
Earlier deliveries aren't included because the labeler code variable has spaces.
A constructed variable indicating the type of NDC: 4-4-2, 5-3-2, or 5-4-1 is included.